A liquid biological sample such as blood is typically taken from a patient using a fingerstick or withdrawn with a syringe or a sealed vacuum tube. The biological sample often needs to be transferred from an open site, such as a droplet formed from fingerstick or from an opened sample tube, for diagnostic analysis. Typically, a micro capillary tube or a simple blood transfer device is used for transferring and dispensing the biological sample. However, existing simple blood transfer devices utilizing capillary action have various deficiencies and are not convenient to use.
One commonly used device for delivering a specific volume of a blood sample is Aqua Cap™ manufactured by Drummond Scientific Inc. This device is a glass capillary tube with a liquid tight plunger, positioned half way in the glass tube. A blood sample is taken via capillary action to the position of the plunger. The blood sample is dispensed by pressing the plunger using a plunger rod that is inserted into the glass tube by the user. Due to the small dimension of the capillary tube, it is difficult for the user to insert the plunger rod into the capillary tube for each use. Moreover, the plunger rod can be easily entered from a wrong direction.
Another commonly used device is a glass capillary tube connected at one end to a reusable rubber bulb. The user needs to connect the rubber bulb to the glass capillary tube before use and remove the rubber bulb from the contaminated glass capillary tube after dispensing a sample. This device requires substantial skill of the user in order to deliver a desired amount of a sample. Moreover, manual disassembly of the contaminated glass capillary tube after each use exposes the user to a high risk of contamination by the biological samples.
Therefore, there is a need for an improved capillary micropipette that overcomes the above mentioned deficiencies.